[postgis-devel] Astronomical extensions

Markus Schaber schabi at logix-tt.com
Thu Nov 2 05:35:45 PST 2006


Hi, Jim,

Jim Bosch wrote:

> -    Astronomers deal with ellipses, and often care very much about
> ellipse-specific things.  While approximating ellipses as polygons is
> perfectly fine for topological operations (so there's no need to worry
> about multi-ellipses, etc.), being able to extract things like
> ellipticity and orientation angle from individual ellipses is of utmost
> importance.  So I'd need to make an ellipse data type, and add the
> necessary operators for it to interact sensibly with existing PostGIS
> types.  I'm not sure, however, whether I should make this a new subtype
> of the PostGIS Geometry type, or a new PostgreSQL type altogether.
> There are probably a host of other more subtle questions as well.

In case you're going to extend the PostGIS types, please see whether
there are any OpenGIS standards one can implement or ignore :-)

> -    Astronomers use a totally different set of coordinate systems.  A
> very basic gnomonic projection is by far the most common, but it is
> described very differently (not to mention the fact that everything is
> inside-out, since we look at the sky, not the ground).  The astronomical
> community already has a large set of standard coordinate systems and
> standard representations for them, as well as several libraries (similar
> to PROJ4 in nature) to do the actual transformations.  This step, then,
> at least seems straightforward: add one of these libraries as an
> alternate backend for transforms, and find a way to put the astronomical
> coordinate systems in the spatial reference table.

What about adding the transformations to proj4?

HTH,
Markus
-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

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